The Norwegian Coastal Administration is still considering how to handle certain aspects of the tunnel design before the construction begins, probably in 2018. Planners are determining how to help ships navigate through the tunnel and how to prepare for such emergencies as collisions or fires. www.nordwest3d.com
Norwegian officials are asking their engineers to combine their seafaring and tunnel-building skills to construct what may be the world’s first tunnel designed expressly for ships.
June 11, 2013—Centuries ago when rough seas made navigating around a Norwegian peninsula too dangerous, Vikings hauled their boats ashore and carried them over land until they reached water again. Years later, Norwegian engineers would become renowned tunnel experts, designing hundreds of tunnels that extend through the country’s rugged terrain.
Now Norwegian seafaring prowess and tunnel-building expertise are expected to merge as the government plans to build what may be the world’s first ship tunnel, a passage large enough to enable cargo ships and commuter vessels to avoid the notoriously treacherous waters around the Stadlandet peninsula, which is north of Bergen slightly southwest of Ålesund, and experience safer, faster trips.
In April the Norwegian government approved NKr 1.6 billion (more than U.S.$300 million) for the Stad Ship Tunnel. Construction is not expected to begin until 2018 and could take four to five years. Jarle Strand, the chief engineer of the Norwegian Coastal Administration, said the tunnel’s total cost might be closer to NKr 2 billion (U.S.$340 million), making it the agency’s largest project ever. Strand wrote in reply to questions posed by Civil Engineering online.
The tunnel is included in a recent update of a report entitled Proposed Norwegian National Transport Plan 2014–2023, which establishes infrastructure priorities in transportation. Norway’s parliament is expected to approve the tunnel this month, Strand said, although the government will have to approve the final design.
The tunnel around the Stad peninsula on Norway’s West Coast
will likely be the world’s first for large cargo ships, and will
accommodate boats weighing up to 16,000 tons. While accustomed
to designing vehicular tunnels, Norwegian engineers have never yet
considered how to design a 1,700 m ship tunnel that is 49 m in
height, the coastal administration says. Norwegian Coastal
The 1,700 m Stad Ship Tunnel would accommodate high-speed passenger ferry service between Bergen and Ålesund and would aid the region’s fishing industry, which sometimes encounters delays because of rough waters.
The design calls for a tunnel 50 m high and 36 m wide that would reach a depth of 12 m below the sea surface. A tunnel that size would require the removal of more than 3 million m3 of rock from the tunnel, and this amount of rock, once drilled and blasted, would take up 4.5 million m3 of space. So Strand says that the contractors will permanently relocate much of that rock, placing it near the tunnel’s entrance to create two small islands at which travelers could dock their boats and stretch their legs in nice weather.
Strand said that in building the tunnel engineers would probably use the same techniques that are employed in road tunnels, including drilling and blasting with dynamite, but he noted that constructing a tunnel large enough to accommodate a 16,000-ton cargo ship would present new challenges. Norwegian contractors have “not built tunnels so long, with this height, and . . . where we are under the sea surface,” he said.
Planners are still wrestling with such questions as how to help ships make their way through the tunnel and how to plan for such emergencies as collisions and fires. The Norwegian Coastal Administration is also considering whether to answer the remaining design questions in-house or leave them to the contractors. The contractors have not yet been chosen, although Strand said they would probably come from Norway and the European Union.
“We’re still planning and we also have to make further analysis of different things,” Strand said, including the characteristics of the tunnel rock, which will be evaluated by means of drill tests.
Builders would begin the drilling from above and would establish the tunnel’s profile and radius before drilling farther down. The work would proceed from the center outward. Crews would remove both ends of the tunnel last, letting water pour in from the adjacent fjords after most of the work was done.
To secure the rock inside the tunnel, the Norwegian Coastal Administration plans to use 30,000 bolts, which will range in length from 6 m to 15 m. According to documents prepared by the agency, more than 30,000 m3 of concrete would be sprayed for reinforcement.
Randi Paulsen Humborstad, a senior adviser to Nordfjord Vekst, an organization promoting the project because of its economic benefits, says the tunnel would also improve safety on local waters that have claimed 33 lives in dozens of accidents since World War II.
In addition to allowing for the more efficient passage for cargo
ships, the tunnel will also accommodate a high-speed commuter
ferry between the towns of Bergen and Ålesund. Norwegian Coastal
A statement from the Norwegian Coastal Administration says that in bad weather high waves collide from different directions and that the waters remain treacherous even days after the winds have subsided. “The combination of ocean currents and underwater topography creates particularly complex and unpredictable waves,” the statement says. In 2004 the Midnatsol, a ship carrying 161 passengers for the tourist line Hurtigruten, became stranded in dangerous waters. The ship did not go down, but the incident underscored the perils of navigation in the area.
The safer navigation offered by the tunnel would probably be a boon to the region economically, Paulsen Humborstad says, since high waters can delay fishing industry shipments, including those of the internationally known salmon fishery Marine Harvest.
“In Norway the sea is the backbone of transport,” Paulsen Humborstad says. “We think [the tunnel] will boost the economy in the communities along the coast.”